Computers implanted in brain could help paralyzed

SCIENCE

Published 4:00 am, Tuesday, December 27, 2011

Photo: Kendra Luck, The Chronicle

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Photo: Kendra Luck, The Chronicle

Computers implanted in brain could help paralyzed

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It sounds like science fiction, but scientists around the world are getting tantalizingly close to building the mind-controlled prosthetic arms, computer cursors and mechanical wheelchairs of the future.

Researchers already have implanted devices into primate brains that let them reach for objects with robotic arms. They've made sensors that attach to a human brain and allow paralyzed people to control a cursor by thinking about it.

In the coming decades, scientists say, the field of neural prosthetics - of inventing and building devices that harness brain activity for computerized movement - is going to revolutionize how people who have suffered major brain damage interact with their world.

"Medicine has not taken neural prosthetics very seriously until recently," said Dr. Edward Chang, a UCSF neurosurgeon and co-director of the Center for Neural Engineering and Prostheses at UC Berkeley and UCSF. "But it's become clear in the last five to 10 years that there are some practical applications."

Jose Carmena, a neuro-engineer at UC Berkeley and Chang's co-director, puts his thoughts more succinctly: "There's going to be an explosion in neural prosthetics."

The joint UC Berkeley and UCSF center started a year ago to take advantage of the neurology expertise in San Francisco and the engineering skills across the bay.

Such devices that allow the brain to control a device aren't entirely new. Aside from some small steps made at other institutions - the brain-controlled computer cursor, for example - there's the cochlear implant, the first neural prosthetic tool developed and the only one that's ever seen wide use.

The cochlear implant, which was invented at UCSF in the 1970s, intercepts sounds as electrical signals and then sends those signals directly to the brain, bypassing the damaged nerves that caused hearing loss. The devices being developed today work under the same premise but are much more complex.

Over the past decade, scientists have made leaps of progress in learning how to read and decode the millions of electronic impulses that fire between neurons in the brain, controlling how our bodies move and how we see, feel and relate to the world around us.

Imagine, for example, the neural effort required just to pick up a glass of red wine, Carmena said.

Vast amount of details

It's not enough just to prompt the right muscles to move an arm. Millions of signals in the brain help us determine where our own arm is in relation to our body, so our hand doesn't grope wildly for the glass. Our brains sense that it's a delicate glass that must be picked up carefully, pinched between fingers. The neurons control how fast our arm moves, making sure the wine doesn't slop over the edges.

That's an astronomical amount of communication happening, all in fractions of a second, without our even being aware of it. In fact, it's more communication than our best smart-phone technology can handle.

"We don't have existing electronics to be able to process in real time dozens of channels from the brain," Chang said. "It turns out we need a lot of information from the brain to work."

The neural prosthetic devices that are just in their infancy now work by connecting a device inserted into the brain directly to a computer. The signals from the brain, in the form of electrical impulses, travel through a cable to the computer, where they are decoded into instructions for some kind of action, like moving a cursor.

But for a neural prosthetic device to actually be useful, it would have to be transplanted near or in the brain and transmit wireless signals to a device like a robotic arm. It would need to be able to last forever - or at least a lifetime - on batteries that never have to be changed and won't damage the brain.

Other problems are going to require an even deeper understanding of how the brain works. Scientists don't yet know what parts of the brain would be best suited for implanting a device to read electrical signals - or even whether an implanted device would work better than one that's attached to the brain's surface.

It's possible that a surface device could collect enough information to be useful in controlling a neural prosthesis with much less risk to the patient.

'Sense of ownership'

But it may be that scientists need to implant a device into the brain to collect enough of the brain signals, especially for creating a prosthetic device that feels natural - a robotic arm, perhaps, that can sense hot and cold, or the difference between a wine glass and a coffee mug.

"You want the arm to feel like it's a part of you, not this thing you're picking up," Sabes said. "It will increase the sense of ownership of the device."

A major part of Chang's research is determining what devices would actually be useful to patients. He knows that some scientists are studying exoskeletons that may allow paralyzed people to walk someday, but he wonders if that's a truly feasible device.

Patients may be better served by a simple computer cursor that is highly responsive to their minds and doesn't require intense, focused concentration to move, Chang said. For a person who is completely paralyzed, just being able to send and read e-mails may be life changing.

"Controlling a robotic body, that's the dream. But it's not my dream," Chang said. "I'm not sure that kind of thing is the most useful for people. I want to find out what are the things that are going to be most useful for people, and it may be as simple as communication."

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